1. Field of the Invention
The invention relates generally to the field of microelectronic fabrication. More particularly, the invention relates to improving the yield and line width performance of liquid polymers.
2. Discussion of the Related Art
Lithography is one of the major drivers of semiconductor industry in its relentless progress in achieving smaller feature sizes with improved yields. More specifically, improved critical dimension (CD) control and reduced process-induced defect and particle counts need to be satisfied simultaneously.
The xe2x80x9cdevelopxe2x80x9d fluid module process plays a significant role in the patterning of increasingly smaller line widths. Regions of high and low dissolution rates are created on the resist film as a result of the sequence of photolithography process steps preceding the develop process. During a develop process, images transferred to the resists film are developed into three-dimensional structures by a wet process. The subsequent etch process (mostly dry) transfers this image onto the substrate (Si, SiO2, poly Si, etc.).
There are many variations of a good develop process. In general, a typical develop process has two main parts. In the first part, developer fluid is dispensed over a wafer spinning at a low rpm followed by a static puddle formation and a long static or oscillating step at which regions of high dissolution rate are etched away, creating 3-dimensional images on the film. Quality of patterned images, value of side wall angles and CD control, are all strongly affected by the first part of the develop process. The chemical wet etch step is immediately followed by a deionized (DI) water rinse step whose main function is to wash away dissolved resist and developer fluid mixture with minimum particle and defect count on the patterned wafer. Naturally, the rinse step is extremely crucial in improving yield of a lithography process.
Heretofore, the requirements of improved critical dimension control, reduced process-induced defect counts and reduced process-induced particle counts referred to above have not been fully met. What is needed is a solution that simultaneously addresses all of these requirements.
A primary goal of the invention is to improve yield. Another primary goal of the invention is improved CD control capability. This invention provides a solution for both of these problems in the developer fluid module of a wafer track tool.
A first aspect of the invention is implemented in an embodiment that is based on a method for minimizing precipitation of developing reactant by lowering a sudden change in pH, said method comprising: developing at least a portion of a polymer layer on a substrate with a charge of developer fluid; then permitting at least a portion of said charge of developer fluid to dwell on said polymer so as to controllably minimize a subsequent sudden change in pH; and then rinsing said polymer with a charge of another fluid.
A second aspect of the invention is implemented in an embodiment that is based on a method for minimizing precipitation of developing reactant by lowering a sudden change in pH, said method comprising: developing at least a portion of a polymer layer on a substrate with an initial charge of a developer fluid; then rinsing said polymer with an additional charge of said developer fluid so as to controllably minimize a subsequent sudden change in pH; and then rinsing said polymer with a charge of another fluid.
A third aspect of the invention is implemented in an embodiment that is based on a method for minimizing precipitation of developing reactant by lowering a sudden change in pH, said method comprising: developing at least a portion of a polymer layer on a substrate with a charge of developer fluid; then contacting said substrate with a charge of buffer, thereby mixing at least a portion of said developer fluid with at least a portion of said charge of buffer, so as to controllably minimize a subsequent sudden change in pH; and then rinsing said polymer with a charge of another fluid.
A fourth aspect of the invention is implemented in an embodiment that is based on an apparatus for minimizing fluid impingement force on a polymer layer to be developed on a substrate, thereby improving yield and line width control performance, said apparatus comprising: a nozzle including: a manifold adapted to supply a fluid; a plurality of fluid conduits coupled to said manifold; and a plurality of tubular inserts located within said plurality of fluid conduits.
A fifth aspect of the invention is implemented in an embodiment that is based on an apparatus for minimizing fluid impingement force on a polymer layer to be developed on a substrate, thereby improving yield and line width control performance, said apparatus comprising: a nozzle including: a developer manifold adapted to supply a developer fluid; a plurality of developer fluid orifices coupled to said developer manifold; a rinse manifold adapted to supply a rinse fluid; and a plurality of rinse fluid orifices coupled to said developer manifold, wherein said developer manifold and said rinse manifold are staggered to reduce an exterior width of said nozzle.
A sixth aspect of the invention is implemented in an embodiment that is based on an apparatus for minimizing fluid impingement force on a polymer layer to be developed on a substrate, thereby improving yield and line width control performance, said apparatus comprising: a nozzle including: a developer manifold adapted to supply a developer fluid; a plurality of developer fluid orifices coupled to said developer manifold; a rinse manifold adapted to supply a rinse fluid; a plurality of rinse fluid orifices coupled to said rinse manifold, and said plurality of rinse fluid orifices arranged to define at least one rinse fluid axis, wherein said nozzle is connected to a bracket adapted to raise and lower said nozzle with regard to said substrate and reposition said at least one rinse axis so as to be substantially coplanar with a normal to a center of said substrate.
Another aspect of the invention is to provide a method for achieving a uniform, quasi-equilibrium succession of states from the introduction of developer chemical to the wafer surface, to its removal. This and other aspects are provided in an embodiment by dispensing a substantially inert material onto a wafer surface prior to dispensing developer fluid, inducing a flow of developer fluid across a portion of a wafer surface for a time interval greater than a transit time for a fluid element to reach an outer wafer edge, the time interval prior to the substantial completion of the developing chemical reaction, dispensing a fresh charge of developer fluid over the wafer after a developing chemical reaction has proceed substantially to completion, and dispensing a substantially inert material over a wafer subsequent to dispensing the fresh charge of developer fluid.
These, and other, goals and aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such modifications.